#include <iostream>
#include <vector>
using namespace std;

const int maxn = 1e5+5;
int n,k,a,retailer[maxn] = {0};
double p,r,sum = 0;
vector<int> g[maxn];

void dfs(int u,double price){
    if(retailer[u])    sum += retailer[u]*price;
    for(int i=0;i<g[u].size();i++)
        dfs(g[u][i],price+price*r);
}

signed main()
{
    cin>>n>>p>>r;
    r = r/100;
    for(int i=0;i<n;i++){
        cin>>k;
        if(k==0)    cin>>retailer[i];
        for(int j=0;j<k;j++){
            cin>>a;
            g[i].push_back(a);
        }
    }
    dfs(0,p);
    printf("%.1f",sum);
    return 0;
}
